> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mermail.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Chat with mailbox agent

> **Plans:** `Free` · `Developer` · `Enterprise`

Streams an AI agent chat turn for a mailbox conversation. Response is an AI SDK UI message stream (not a plain JSON object). The latest message must be from the user. Duplicate message ids return `409`.

**API credits:** 25 (ai_heavy).



## OpenAPI

````yaml /openapi/openapi.json post /api/agent/mailbox
openapi: 3.1.0
info:
  title: Mermail API
  version: 1.0.0
  description: >
    Programmatic Mermail API for scripts, agents, and integrations.


    ## Authentication


    Authorize with an API key from **Settings → API Keys**:


    ```

    x-api-key: sk-proj-…

    ```


    ## Plans


    Each endpoint page shows plan badges (**Public**, **All plans**, or
    **Developer+**). Free can call the core catalog; Developer-gated paths need
    Developer or Enterprise.


    ## Try it


    Every endpoint page includes an interactive playground. Click **Try it**,
    paste your API key into the `x-api-key` field, fill path/query/body fields
    (prefilled from examples), and send a live request to
    `https://console.mermail.app`. You can also copy the generated cURL /
    JavaScript / Python snippet.


    ## Credits


    | Class | Cost |

    | --- | ---: |

    | read | 1 |

    | write | 2 |

    | email_send | 5 |

    | provision | 10 |

    | ai_light | 15 |

    | ai_heavy | 25 |
  contact:
    name: Mermail
    email: contact@mermail.app
    url: https://mermail.app
servers:
  - url: https://console.mermail.app
    description: Production
security:
  - apiKeyAuth: []
tags:
  - name: Public
    description: No authentication
  - name: Usage
    description: Credits and email quotas
  - name: Workspaces
    description: Workspaces, members, storage
  - name: Domains
    description: Custom email domains (Developer+)
  - name: Mailboxes
    description: Agent inboxes
  - name: Emails
    description: Send, list, search, folders
  - name: AI agent
    description: Mailbox agent chat
  - name: Task triage
    description: Task triagers (all plans)
  - name: RAG
    description: Knowledge documents and recall
  - name: Integrations
    description: Composio, Telegram, push
  - name: Affiliate
    description: Affiliate program
paths:
  /api/agent/mailbox:
    post:
      tags:
        - AI agent
      summary: Chat with mailbox agent
      description: >-
        **Plans:** `Free` · `Developer` · `Enterprise`


        Streams an AI agent chat turn for a mailbox conversation. Response is an
        AI SDK UI message stream (not a plain JSON object). The latest message
        must be from the user. Duplicate message ids return `409`.


        **API credits:** 25 (ai_heavy).
      parameters: []
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
                - mailboxId
                - conversationId
                - messages
              properties:
                mailboxId:
                  type: string
                  example: support@mail.acme.com
                conversationId:
                  type: string
                  example: conv_01
                messages:
                  type: array
                  items:
                    type: object
                    additionalProperties: true
                  description: AI SDK UIMessage array (id, role, parts)
                thread_id:
                  type: string
                  nullable: true
                trigger:
                  type: string
                  enum:
                    - submit-message
                    - regenerate-message
            example:
              mailboxId: support@mail.acme.com
              conversationId: conv_01
              messages:
                - id: u1
                  role: user
                  parts:
                    - type: text
                      text: What needs a reply?
              trigger: submit-message
      responses:
        '200':
          description: UI message stream
          content:
            text/plain:
              schema:
                type: string
              example: (streaming AI SDK UI message response)
        '400':
          description: Latest message is not from the user, or invalid body
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
              example:
                error: Invalid request
        '401':
          description: Missing, invalid, expired, or revoked API key / token
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
              example:
                error: Unauthorized
        '402':
          description: API credits exhausted for this workspace period
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
              example:
                error: Invalid request
        '403':
          description: Forbidden — plan gate, wrong workspace, or missing role
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
              example:
                error: Forbidden
        '409':
          description: Duplicate message submit
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
              example:
                error: Conflict
        '429':
          description: Rate limit exceeded (workspace RPM or email send limits)
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
              example:
                error: Too many requests
          headers:
            Retry-After:
              schema:
                type: integer
              description: Seconds until the rate limit window resets
      security:
        - apiKeyAuth: []
components:
  schemas:
    Error:
      type: object
      required:
        - error
      properties:
        error:
          type: string
          example: Unauthorized
        code:
          type: string
  securitySchemes:
    apiKeyAuth:
      type: apiKey
      in: header
      name: x-api-key
      description: >-
        API key (`sk-proj-…`) from Settings → API Keys. Required for sold API
        calls outside the Mermail console.

````